The following project proposes to use the research tools of electron microprobe analysis and electron diffraction upon the previously unexplored area of bone resorption. Microprobe and diffraction studies will first be performed on anhydrously processed fetal rat long bones. Relative elemental microprobe quantitations and electron diffraction patterns will be performed on selected areas of bone, both associated and not associated with cells implicated in the resorption process, (osteoclasts, osteoblasts, fibroblasts). Similar quantitations will be made upon areas of calcification within these cell types. Additional quantitative data will be obtained through element dot mapping of these areas. Such quantitations may aid in determining where and to what extent various cells, and portions of cells, are responsible for the bone resorption process. These quantitative techniques will then be applied to the monocyte - bone fragment system in order to determine the area of monocyte responsible for bone resorption.